Over the past few decades conventional armor technologies have proven ineffective in protecting against explosively formed projectiles (EFPs). An EFP is a special type of shaped charge designed to penetrate armor. It usually consists of a hardened metal canister containing a high explosive charge. One end of the canister is capped with a less dense metal such as copper. When the charge is ignited the copper end becomes molten and is forced apart of the canister. If the composition of the copper and charge is calibrated correctly, the material will elongate into a molten jet projectile during the explosion.
The resulting projectile can travel up to several kilometers a second and literally melt through conventional armor. In its most destructive form, an EFP forms multiple projectiles which impact the armor in successive slugs; these successive slugs are spaced a very small fraction of a second apart, so that each subsequent slug impact the target at the same spot as the preceding one, thereby benefiting from each previous slug's partial penetration of the target. Within conventional plate armor, the intense heat of a projectile slug instantaneously solidifies and stabilizes the route of entry for successive slugs. Multiple projectile EFPs can penetrate even the heaviest conventionally armored vehicles.
The vulnerability of conventional armored vehicles against EFPs is particularly evident in Iraq. In 2007 an entirely new vehicle program was begun to combat the increasing threat from EFPs. The vehicles in this program, called Mine Resistant Armor Protected II (MRAP II), are upgrades on an existing class of vehicles (MRAP I) which were at one time considered adequate to protect US forces from shaped charges.
The predominant design strategy for new MRAP I and MRAP II vehicles as well as other vehicle initiatives involves applying increased quantities of conventional armor to heavier chassis. Although this strategy typically meets the protection goals, it carries at least four significant drawbacks.
First, what were once considered “light” armored vehicles now carry upwards of five to six thousand additional pounds of armor. This not only adds significant costs, but also begins to defeat the purpose of having a “light” vehicle in the first place. Second, the additional weight naturally makes these formerly light vehicles difficult and expensive to transport. Third, these vehicles are typically manufactured in a permanent configuration. Thus, once a vehicle's armor is damaged, the entire vehicle must be taken out of operation for repairs. Fourth, since the vehicles are deployed in a permanent configuration, they are inherently inflexible to changing threats. If a vehicle is designed to respond to a particular threat and that threat changes, the vehicle's utility is greatly diminished.